ARM64: dts: meson-gx: consistently use the GIC_SPI and IRQ type macros

the mailbox and ethmac nodes used the magic number "0" instead of the
GIC_SPI preprocessor macro. Additionally the ethmac used the magic
number "1" instead of IRQ_TYPE_EDGE_RISING.
Fix this to make the .dtsi easier to read.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>